1. For Office 365 I think it will be renewed automatically once you have keyed in you credit card detail.

2. Not sure how to check from desktop PC, but if you have a Windows Phone you can go to Windows Store and check.

3. Currently only 950 and 950XL support continuum. There are some Chinese-made and Japanese-made Windows phones that support continuum with affordable prices (ie they use lower speed chips like qualcom 6xx). I read that one Windows Mobile phone made by a HK company with affordable price will be coming soon to Malaysia.

4. Windows Mobile 10 is continually updated. I think for newer devices, it is best to go for Windows 10.

Windows Mobile will still be updated because it is part of Windows 10 family. For the lack of apps I hope the situation will improve with Universal Windows Platform, where an app can run on PC, mobile, hololens, Xbox etc as long as it runs Windows. Right now, most services can be accessed by using a browser.

Well, for me, I have the apps I want for Windows Mobile. My attraction to use is not a huge selection of apps but the familiarity. I own 3 phones - Lumia 950, iPhone 6 and Oppo (Android). I think each has their own strength. Many popular apps like Whatsapp, Facebook, Instagram are cross platforms and available on all three platforms. Only Google services does not have a presence on Windows Mobile. My personal feeling is that because Microsoft and Google compete with each other.

Let's hope things will get better as Microsoft improves the operating system because right now Microsoft is releasing updates as frequent as they release update for Windows on PC.

I think in the future icons and apps will no longer that important. Their roles will be taken over by digital assistant like Siri, Cortana and Google Now. I am impressed with Siri. Sadly I cannot try Cortana.

Outlook on Windows Mobile can be configured to receive and send emails from Gmail. In fact, I think Outlook is a better solution than gmail app on Android for me because I have multiple email clients like Yahoo, Outlook and one for my university email.
As for YouTube, there are many third parties YouTube clients on Windows Store. Many can even download the video to watch when you don't have internet access or just want to save your data quota. Plus you have no ads. I use MyTube.